Low-Dose Chidamide Treatment Displays Sex-Specific Differences in the 3xTg-AD Mouse

Abstract

Epigenetic compounds have become attractive small molecules for targeting the multifaceted aspects of Alzheimer's disease (AD). Although AD disproportionately affects women, most of the current literature investigating epigenetic compounds for the treatment of AD do not report sex-specific results. This is remarkable because there is rising evidence that epigenetic compounds intrinsically affect males and females differently. This manuscript explores the sexual dimorphism observed after chronic, low-dose administration of a clinically relevant histone deacetylase inhibitor, chidamide (Tucidinostat), in the 3xTg-AD mouse model. We found that chidamide treatment significantly improves glucose tolerance and increases expression of glucose transporters in the brain of males. We also report a decrease in total tau in chidamide-treated mice. Differentially expressed genes in chidamide-treated mice were much greater in males than females. Genes involved in the neuroinflammatory pathway and amyloid processing pathway were mostly upregulated in chidamide-treated males while downregulated in chidamide-treated females. This work highlights the need for drug discovery projects to consider sex as a biological variable to facilitate translation.

Keywords: 3xTg-AD mouse; Alzheimer’s; HDAC inhibitor; epigenetics; sex differences.

Figure 1

Glucose tolerance is significantly improved in chidamide-treated males. (A) Glucose tolerance testing in males and females at 10 months of age. (B) Insulin tolerance testing in males and females at 12 months of age. The graphs represent mean ± SEM. Unpaired Student’s t-test or Mann–Whitney test was used for comparisons of two means; * p < 0.05; n = 3–5/group.

Figure 2

AD pathological hallmarks show sex-, treatment- and brain region-dependent differences. Levels of total tau and phosphorylated tau species in the (A) hippocampus and (B) PFC. Levels of Aβ-40 and -42 in the (C) hippocampus and (D) PFC. The graphs represent mean ± SEM. Unpaired Student’s t-test or Mann–Whitney test was used for comparison between treatments within sex. Tukey’s multiple comparisons test was used for comparison between sexes within treatment groups. ** p < 0.01 for significance between treatment groups within sex; # p < 0.05, ## p < 0.01 for significance between sex within treatment groups; n = 3–5/group.

Figure 3

Significant differentially expressed genes between chidamide and vehicle separated by sex (A). Males showed greater DEGs in response to chidamide treatment than females. Pathway analysis shows a majority of pathways, including the neuroinflammatory pathway and amyloid processing pathway, are upregulated in male chidamide-treated mice compared to vehicle-treated males, while a majority of pathways are downregulated in female chidamide-treated mice compared to vehicle-treated females (B). NanoString data analyzed using nSolver Analysis Software 4.0; heatmaps created with Morpheus Software.

Figure 4

Long-term, low-dose chidamide treatment shows differing and sometimes opposing sex-dependent responses in AD- and metabolism-related gene expression. AD-related genes in the (A) hippocampus and (B) PFC. (C) Glucose transport genes in the hippocampus. The graphs represent mean ± SEM. Unpaired Student’s t-test or Mann–Whitney test was used for comparisons of two means. Tukey’s or Dunnett’s multiple comparisons test was used for comparison between sexes within treatment groups. * p < 0.05, **** p < 0.0001 for significance between treatment groups within sex; # p < 0.05, ## p < 0.01 for significance between sex within treatment groups; n = 3–5/group.